As shown in FIG. 1, in most vehicles, a fuel level sending unit 10 is utilized to measure the level of fuel 14 in a fuel tank 18. Typically, the fuel level sending unit 10 is mounted on a fuel pump module 20 and includes a float 22 that is buoyant in the fuel 14, and a pivot arm 26 connecting the float 22 with a wiper 30 of a variable resistor or potentiometer 34. The potentiometer 34 provides an electrical signal to operate a display (not shown) so that an operator can monitor the fuel level in the fuel tank 18 of a vehicle. The electrical signal provided by the potentiometer 34 is proportional to the position of the float 22 as the fuel level in the fuel tank 18 changes.
The potentiometer 34 typically includes a resistor plate 38 having one or more elongated electrical resistor paths 42 that are connected across a supply voltage. The wiper 30 is movable along the resistor paths 42 and is in electrical contact with the resistor paths 42. Typically, the resistor paths 42 are laid out along an arcuate pathway and the wiper 30 is mounted for rotation substantially about the center of the arcuate resistor paths 42.
One or more contact buttons 46 are usually coupled to the wiper 30 for sliding and electrical contact with the resistor paths 42. FIGS. 2–4 illustrate a prior art contact button 46. Conventional contact buttons 46 may sometimes be in the form of a conductive metal rivet or other cylindrical body having a substantially curved or semi-spherical surface 50 in contact with the resistor path 42. The conventional contact button 46 includes a head 54 and a shank 58 extending from the head 54. In some constructions of the conventional contact button 46, the head 54 includes a diameter dimension D of about 2.8 mm. The surface 50 has a substantially semi-spherical contour, and a portion of the surface 50 is in sliding contact with a respective resistor path 42. In some constructions of the conventional contact button 46, the surface 50 defines a radius of about 3.0 mm. Also, in some constructions of the conventional contact button 46, a blend radius 62 is defined between the surface 50 and the upper portion of the head 54. Such a blend radius 62 can be about 0.9 mm. In the illustrated construction of FIGS. 2–4, the conventional contact button 46 is in the form of a rivet, with the shank 58 being at least partially deformable to secure the contact button 46 to the wiper 30.